JP5352965B2 - Rack manufacturing method - Google Patents

Abstract

A light-weight structure capable of sufficiently ensuring any of the width size, strength and rigidity of a rack tooth (10), and a production method thereof. A rack tooth (10) is formed by plastic working on one side surface in the radial direction of a part in the axial direction of a sectionally circular rod unit (9). The radius of curvature of the section shape of a portion deviated in the circumferential direction from a rack-tooth (10) forming portion is set to be larger than the radius of curvature of the section shape of an outer circumferential surface of the remaining part in the axial direction of the rod unit (9). For this purpose, as shown by (A)->(B), the part in the axial direction and the remaining part in the circumferential direction are formed into a partially cylindrical surface portion (17) having a radius of curvature larger than that of the outer circumferential surface of a material (13) while a portion in the axial direction of the material (13) and a portion in the circumferential direction are being crushed, thereby defining an intermediate material (20).Then, as shown by (C)->(D), the above rack tooth (10) is formed at a portion in the axial direction ofthe intermediate material (20) and a portion in the circumferential direction. Finally, as shown by (E)->(F), it is subjected to sizing to complete a rack (8).

Description

  The present invention relates to an improvement in a manufacturing method of a rack that is incorporated in a steering gear that constitutes, for example, an automobile steering device and pushes and pulls a tie rod with an axial displacement. Specifically, an object is to realize a manufacturing method capable of obtaining a rack having sufficient rigidity and strength at low cost.

  For example, in a steering device for giving a steering angle to a steering wheel of an automobile as shown in FIG. 30 (generally a front wheel except a special vehicle such as a forklift), a steering shaft that rotates as the steering wheel 1 is operated. 2 movement is transmitted to the input shaft 6 of the steering gear 5 through the universal joints 3 and 3 and the intermediate shaft 4. The steering gear 5 includes a pinion that is rotationally driven by the input shaft 6 and a rack that meshes with the pinion. When the pinion rotates together with the input shaft 6, the rack is displaced in the axial direction, and a pair of tie rods 7, 7 coupled to both ends thereof are pushed and pulled to give a desired steering angle to the steered wheels.

  If a rack for a steering gear as described above is made by cutting a material to form rack teeth, it is difficult to ensure the strength and rigidity of the rack teeth at a rate that increases the manufacturing cost. On the other hand, if the rack teeth are processed by plastic deformation of the material, the time required for processing the rack teeth can be shortened, the manufacturing cost can be reduced, and the resulting metal structure of the rack teeth becomes dense. Therefore, it is easy to ensure the strength and rigidity of the rack teeth. As described above, the inventions described in Patent Documents 1 to 4 are conventionally known as inventions related to a rack in which rack teeth are processed by plastic deformation and a manufacturing method thereof.

  Of these, in Patent Documents 1 and 2, a circular bowl-shaped material is strongly sandwiched between a pair of molds, and a part of the outer peripheral surface of the material is provided in one of the molds. An invention relating to a method for manufacturing a rack is described in which a concavo-convex shape is transferred to form a rack tooth. The surplus generated by forming the rack teeth (extruded from the portion of the rack teeth that should become the concave portion) is burrs between the molds and from the rack body to the side. Protruding into the shape and removed later.

  In the case of such conventional techniques described in Patent Documents 1 and 2, since the surplus portion protrudes sideways from the main body portion of the rack, the stress generated in the pair of molds that press the rack increases. It is difficult to ensure the life of both molds. In addition, a process for removing the surplus protrusion protruding from the main body part to the side is necessary, and it is inevitable that the manufacturing cost increases. Furthermore, in order to reliably transfer the concave and convex shape provided on the one mold to the material, the plastic working including the transfer is performed so that a large stress is applied to both the molds as described above. Must be performed by hot forging or warm forging. Regardless of whether hot forging or warm forging, the mold will thermally expand due to the temperature rise during processing, but it is difficult to accurately control the amount of thermal expansion, so the accuracy of the rack teeth obtained is sufficient. It is difficult to secure.

In order to solve the inconveniences as described above, in Patent Document 3, a concave portion is formed on the back side of a portion where a rack tooth is to be formed in a circular material, so that the rack tooth is formed. An invention relating to a method for manufacturing a rack is disclosed, in which surplus material generated along with this is released to the recess.
In the case of the prior art described in Patent Document 3 as described above, there is no inconvenience that arises when the prior art described in Patent Documents 1 and 2 is carried out, but instead, the processing of the recesses is necessary, which is also manufactured. It is inevitable that the work is cumbersome and the manufacturing cost increases. In particular, since the concave portion is processed by swaging, lathe processing, or the like, it is difficult to smoothly shift from the concave portion processing to the next rack processing operation (continuous subsequent processing). This also causes a high manufacturing cost. Furthermore, the outer diameter of the portion that does not require much strength and that is axially deviated from the portion where the rack teeth are formed is the diameter of the material required to form the rack teeth that requires strength. As a result, the weight of the entire rack is easily increased.

Further, Patent Document 4 describes an invention relating to a method for manufacturing a rack in which a hollow circular material is expanded in the width direction and rack teeth are formed in the expanded portion.
In the case of the conventional technique described in Patent Document 4 as described above, in order to increase the width dimension of the rack tooth, the amount of the bottom portion of the rack tooth is increased by the amount of the hollow circular tubular material that is expanded in the width direction. The wall thickness tends to be small (thin). For this reason, it is difficult to sufficiently secure the strength of the portion of the rack where the rack teeth are formed.

JP-A-10-58081 Japanese Patent Laid-Open No. 2001-79639 Japanese Patent No. 3442298 JP 2006-103644 A

  In view of the circumstances as described above, the present invention is to realize a manufacturing method that can sufficiently secure the width dimension, strength, and rigidity of the rack teeth and can obtain a rack having a lightweight structure at low cost. Invented.

The rack which is the object of the present invention is made of a metal material, and at least a part of the axial direction is a solid rod having a circular cross section, and the diameter of the part of the rod part which is a solid material in the axial direction. Rack teeth formed by plastic working on one side of the direction.
In particular, the rack that is the subject of the present invention has a radius of curvature of the cross-sectional shape of the portion of the outer peripheral surface of the portion that is a solid material in the axial direction that is deviated in the circumferential direction from the portion where the rack teeth are formed. The radius of curvature of the cross-sectional shape of the outer circumferential surface of the remaining axial portion of the rod portion is larger.

  Further, in any of the rack manufacturing methods of the present invention, in order to manufacture a rack having the above-described configuration, a part of the axial direction of the circular-shaped material to be the rod portion is provided. A partial cylindrical surface having a radius of curvature larger than the radius of curvature of the outer peripheral surface of the material is formed in a part of the axial direction and the remaining part of the circumferential direction while crushing a part of the circumferential direction. The first plastic working is performed to obtain an intermediate material. Then, the rack teeth are formed by a second plastic working in a part of the axial direction and a part of the circumferential direction of the intermediate material.

In particular, in the case of the rack manufacturing method according to claim 1 , in order to manufacture the rack having the above-described configuration, the first plastic working is performed by crushing a part of the material in the axial direction in the radial direction. Thus, a portion of the outer peripheral surface in the axial direction where the rack teeth are to be formed is a flat portion, and the remaining portion outside the flat portion is the cross-sectional radius of curvature of the outer peripheral surface of the material. The upsetting process is a partial cylindrical surface larger than the radius of curvature.
In addition, the second plastic working may be performed from a portion of the intermediate material in the axial direction by a holding hole of a die whose inner surface is smaller than the outer diameter of the intermediate material in the width direction of the flat portion. While supporting the disengaged remaining portion, both ends of the intermediate material in the width direction are pressed by pressing the tooth forming punch having an uneven shape corresponding to the rack tooth to be formed against the flat portion and pushing the intermediate material into the holding hole. The metal material of the portion is moved to the flat portion, and press working is performed to form rack teeth on the flat portion.

In the case of the rack manufacturing method according to claim 2 , in order to manufacture the rack having the above-described configuration, the second plastic working is performed in a plurality of stages, and the rack tooth pressure to be obtained is obtained. After forming a bare rack tooth with a tooth forming punch having a shape corresponding to a pressure angle smaller than the corner, the curvature of the cross-sectional shape of at least the tooth base part or the edge part of the tooth tip part of the width direction ends of the bare rack tooth Perform plastic working to increase the radius. Thereafter, a tooth finishing punch having a shape corresponding to the pressure angle of the rack tooth to be obtained is pressed against the raw rack tooth, and the raw rack tooth is processed into a rack tooth.

Furthermore, in the case of the method for manufacturing a rack according to claim 3 , in order to manufacture a rack having the above-described configuration, the second plastic working causes the axial material portion of the intermediate material to partially The rack teeth are formed in a part of the circumferential direction, and a pair of relief flat surface portions are formed on both sides of the rack teeth, and then sizing is performed to improve the accuracy of the rack teeth. The metal material which moves with this is stopped at the both escape flat surface portions to prevent the surplus wall from projecting radially outward from the virtual cylindrical surface obtained by extending the partial cylindrical surface.

Further, when carrying out the invention described in claims 1 and 3 as described above, for example, the second plastic working is performed in a plurality of stages as in the invention described in claim 2 . First, the raw rack teeth are formed by a tooth forming punch having a shape corresponding to a pressure angle smaller than the pressure angle of the rack teeth to be obtained. Thereafter, a tooth finishing punch having a shape corresponding to the pressure angle of the rack tooth to be obtained is pressed against the raw rack tooth.

Further, when the invention described in claim 2 is carried out, it is preferable that the radius of curvature of the cross-sectional shape of the tooth base part or the edge part of the tooth tip part of the width direction end part of the raw rack tooth is formed by plastic working after completion. It is made larger than the curvature radius of the cross-sectional shape of the edge part of the tooth | gear base part of a rack tooth in the width direction both ends.

Further, as in the invention described in claim 2, it is preferable to perform plastic working to increase the curvature radius of the cross-sectional shape of the root part or the edge part of the tooth tip part at both ends in the width direction of the raw rack tooth. For example, in the previous stage of the second plastic working (meaning from the initial stage to the first half of the second plastic working. It does not mean the work performed prior to the second plastic working). A rack tooth is formed, and a pair of relief flat surface portions are formed on both side portions of the raw rack tooth. Thereafter, plastic working is performed to increase the radius of curvature of the cross-sectional shape of the base portion of the base rack tooth in a state in which both the flat relief surface portions are positioned between the pair of molds. And the metal material which moves with this plastic working is stopped at the both escape flat surface portions, and the surplus wall is prevented from projecting radially outward from the virtual cylindrical surface obtained by extending the partial cylindrical surface.

Further, when the invention described in claims 1 and 2 as described above is carried out, the shape of the rack teeth is adjusted after the second plastic working, for example, as in the invention described in claim 3. Apply sizing.
Further, in this case, for example, rack teeth are formed by the second plastic working, and a pair of relief flat surface portions are formed on both side portions of the rack teeth. After that, sizing is performed to improve the accuracy of the rack teeth, and the metal material that moves along with the sizing is stopped on the two escape flat surface portions, so that the surplus diameter is larger than the virtual cylindrical surface that extends the partial cylindrical surface. Protruding outward in the direction is prevented. The two relief flat surface portions are parallel to each other, for example.

In carrying out the present invention, for example, before the first plastic working, the material is passed through a die so as to reduce the outer diameter of the material except for a part in the axial direction. Then, a preliminary intermediate material in which the outer diameter of a part in the axial direction is larger than the outer diameter of the remaining axial direction, and the first plastic working is performed on the preliminary intermediate material.
Alternatively, after the first plastic working and before the second plastic working, the intermediate material is passed through a die so as to reduce the outer diameter of the intermediate material except for a part in the axial direction. Then, a second intermediate material having a larger outer diameter in the axial direction than that of the remaining axial direction is used, and the second plastic material is subjected to the second plastic working.

According to the rack manufacturing method of the present invention configured as described above, the rack teeth can have sufficient width dimensions, strength, and rigidity, and an outer diameter other than the portion where the rack teeth are formed is necessary. A lightweight rack that does not become larger than that can be obtained at low cost.
First, securing the width dimension of the rack teeth can be achieved by making the width of the portion where the rack teeth should be formed in a part of the rod portion in the axial direction larger than the outer diameter of the remaining axial portion of the rod portion. . In addition, the strength and rigidity can be ensured by making this rod part a solid material. That is, the portion where the rack teeth are to be formed in a part of the rod portion in the axial direction is a cross-sectional shape of the portion that is deviated in the circumferential direction from the portion where the rack teeth are to be formed while expanding the width while crushing the material. Is made larger than the curvature radius of the outer peripheral surface of the material. For this reason, the rack tooth | gear which has a large width dimension to the ratio of the outer diameter of this raw material can be formed. Unlike the rack teeth formed in the portion where the hollow circular tubular material is expanded in the width direction, the portion where the rack teeth are formed is sufficiently thick as in the prior art described in Patent Document 4 described above. Can be secured. The strength and rigidity of the rack tooth portion can be improved by increasing the width dimension and further by increasing the radius of curvature of the cross-sectional shape of the portion deviated in the circumferential direction from the portion where the rack teeth are formed.
Moreover, the fact that the outer diameter other than the portion where the rack teeth are formed does not become unnecessarily large and that a lightweight rack can be obtained is that even when the width of the rack teeth is secured, the axial remaining portion of the rod portion This can be achieved by keeping the outer diameter small.

  Furthermore, it can be obtained at a low cost (manufacturing cost can be reduced). With regard to forming the rack teeth by plastic processing, the excess wall becomes a burr and protrudes outward in the radial direction only by performing simple pre-processing. This can be prevented by reducing the processing load and eliminating the need for post-processing for removing excess material. That is, the portion of the rod portion that forms the rack tooth in the axial direction of the rod portion, and the portion that forms the rack tooth originally crushes a circular section having the same cross-sectional area as the axial remaining portion, By flattening the portion where the rack teeth are to be formed, the width dimension is made larger than the outer diameter of the remaining portion in the axial direction. Therefore, in a state before the rack teeth are formed, a partial cross-sectional area in the axial direction of the rod portion is substantially equal to the cross-sectional area of the remaining axial direction portion. Accordingly, the volume of the material existing in a part in the axial direction of the rod portion where the rack teeth should be formed can be appropriately suppressed, and the surplus wall protrudes in the radial direction as the rack teeth are processed. Absent. The movement of the metal material in the second plastic working for forming the rack teeth is mainly performed from the bottom portion of the rack teeth to the tip portion. For this reason, the processing load for forming the rack teeth can be suppressed to a low level, and the rack teeth can be processed by cold processing, which is easier to ensure accuracy than hot processing or warm processing.

In the manufacturing method of the present invention, all the processing steps can be performed in a state where the inside of the mold is not completely filled with the metal material. In other words, the entire process can be carried out without so-called hermetic molding, and the reaction force applied to each mold from the workpiece in each process, and thus, the stress generated in each of these molds can be kept low. The durability of the mold can be improved and the cost can be reduced from this aspect. Further, the structure of each mold can be simplified and can be formed by a general-purpose press facility. In addition, since the stress generated in each die can be kept low, it is possible to form by cold forging, and since the dimensional change of each die can be suppressed, when processing by hot forging or warm forging. In comparison, the accuracy of the obtained rack can be improved. In particular, according to the invention as set forth in claim 1, the rack, at a sufficiently low cost, yet accurately able to build.

Further, if the shape of the rack teeth is adjusted by sizing or multi-stage molding as in the inventions described in claims 2 and 3 , the rack teeth can be processed with higher accuracy. In the case of performing multi-stage molding of these, as in the invention described in claim 2 , during processing of the raw rack teeth into rack teeth, the root part or the tooth tip at both ends in the width direction of the raw rack teeth are processed. If the edge portion of the portion is plastically deformed, the shape accuracy of the rack teeth obtained can be further improved, and the processing load required in each step can be reduced. Also, when performing multi-stage molding or sizing, if the metal material that moves with multi-stage molding or sizing is stopped on a pair of relief flat surfaces, these multi-stage molding or sizing can be performed without sealing molding. it can. And the stress which arises in a metal mold | die with these multistage shaping | molding or sizing can be restrained low, and the durability of this metal mold | die can be improved.

[First example of embodiment]
1 to 9 show a first example of an embodiment of the present invention corresponding to claim 3 . First, the structure of the rack 8 of this example will be described with reference to FIGS. In the following description, the curvature radius of each surface refers to the curvature radius of the cross-sectional shape of each surface unless otherwise specified.
The rack 8 is made of a metal material such as carbon steel, stainless steel, etc., and is a rod member 9 having a circular cross section, which is a solid material, and a diameter of a part of the rod portion 9 in the axial direction (left portion in FIGS. 1 to 3). A rack tooth 10 formed by plastic working is provided on one side surface in the direction. In the case of this example, the rod portion 9 is integrally formed of the same kind of metal material from the outer peripheral surface to the center portion over the entire length. In addition, a radius of curvature R ₁₁ (see FIG. 4) of the cross-sectional shape of the back surface portion 11 that is partly in the axial direction of the rod portion 9 and deviates in the circumferential direction from the portion where the rack teeth 10 are formed. It is larger than the radius of curvature r ₁₂ (see FIG. 4) of the outer peripheral surface of the circular flange portion 12 which is the remaining portion in the axial direction of the portion 9 (R ₁₁ > r ₁₂ ). Among them, the curvature radius r ₁₂ of the outer peripheral surface of the circular rod portion 12 coincides with the radius of curvature of the original outer peripheral surface of the material. Accordingly, the radius of curvature R ₁₁ of the back surface portion 11 is larger than the radius of curvature of the outer peripheral surface of this material. Then, correspondingly, the width W ₁₀ of the rack teeth 10 (simply compared with the case of forming the rack teeth on the outer peripheral surface of the material) is large.

Next, the manufacturing method of the rack 8 as described above will be described with reference to FIGS.
First, as shown in FIG. 5A, inside a concave groove portion 15 having a circular arc shape in section, in which a circular material 13 made of a metal material such as carbon steel or stainless steel is provided on the upper surface of a receiving die 14. Set (mount). Inner surface radius of curvature R ₁₅ of the recessed groove portion 15, (except for the springback due to the processing force releasing) substantially with the radius of curvature R ₁₁ (see FIG. 4) of the back part 11 match (R ₁₅ ≒ R ₁₁₎ ing.

  Next, as shown in FIG. 5B, the upsetting process in which the material 13 is strongly pressed toward the concave groove portion 15 by the front end surface (lower end surface) of the long press punch 16 along the concave groove portion 15. To do. The shape of the tip surface of the pressing punch 16 is generally a flat surface. However, with respect to the width direction of the concave groove portion 15 (left and right direction in FIG. 5), the concave curved surface has a large curvature radius, or both end portions in the width direction protrude linearly or curvedly toward the receiving die 14 (stationary It can also be a concave shape (such as embrace the upper end of the shape after the embossing). In any case, in the upsetting process shown in FIG. 5B, the portion of the material 13 in the axial direction where the rack tooth 10 (see FIGS. 1 to 4) is to be formed is pushed up and down. In addition to crushing, the width in the horizontal direction is expanded to obtain an intermediate material 20. The intermediate material 20 is present on the outer peripheral surface of the portion, on the side of the partial cylindrical surface portion 17 to be the back portion 11 (see FIGS. 1, 3 and 4), and on the opposite side of the partial cylindrical surface portion 17 in the radial direction of the cross section. And a pair of curved surface portions 19 and 19 having a relatively small radius of curvature that makes these both surface portions 17 and 18 continuous.

Next, the intermediate material 20 is taken out from the concave groove portion 15 of the receiving die 14 and inserted (set) into the bottom portion of the holding hole 22 provided in the die 21 as shown in FIG. The holding hole 22 has a U-shaped cross-sectional shape, and the radius of curvature of the bottom portion 23 substantially coincides with the radius of curvature R ₁₅ of the inner surface of the concave groove portion 15 of the receiving die 14. Further, the inner side surfaces 24, 24 are planes parallel to each other. Further, the upper end opening is provided with a pair of guide inclined surface portions 25 and 25 which are inclined in a direction in which the distance between the upper end openings increases toward the upper side.

  When the intermediate material 20 is set in the holding hole 22 of the die 21, the tooth forming punch 26 is inserted into the holding hole 22 as shown in FIG. 5 (C) → (D). The intermediate material 20 is strongly pushed into the holding hole 22 by the tooth forming punch 26. On the lower surface of the tooth forming punch 26, there are provided corrugated irregularities for forming having a shape commensurate with the rack teeth to be obtained. The intermediate material 20 is constrained by the inner surface of the holding hole 22 except for the flat surface portion 18 where the rack teeth are to be formed. Therefore, when the intermediate material 20 is strongly pushed into the holding hole 22 by the tooth forming punch 26, the flat surface portion 18 of the intermediate material 20 is plastically deformed following the corrugated irregularities, and FIG. (D) and a rack rack 27 having rack teeth 10 as shown in FIG. 6 (A). However, the raw rack 27 in this state has insufficient shape accuracy and dimensional accuracy compared to the completed rack 8 (see FIGS. 1 to 4), and the edges of the rack teeth 10 remain sharp. . Further, since the surplus portion pushed out (from the portion that should become the tooth bottom) with the processing of the rack teeth 10 is strongly pressed against the inner side surfaces 24, 24 of the holding hole 22, the left and right sides of the base rack 27 are left and right. Relief flat surface portions 28, 28 parallel to each other are formed on both side surfaces.

  Therefore, after raising the tooth forming punch 26, the raw rack 27 is taken out from the holding hole 22, and as shown in FIG. 5E, a sizing uneven surface portion formed on the upper surface of the sizing die 29 is formed. 30. At this time, the raw rack 27 is turned upside down. The sizing uneven surface portion 30 has a shape that matches the shape of the rack tooth 10 to be obtained, including the chamfered portion of the edge of the tooth (the unevenness is inverted with respect to the completed shape). Therefore, as shown in FIGS. 5E to 5F, the pressing die 31 strongly presses the portion of the base rack 27 where the rack teeth 10 are formed toward the sizing uneven surface portion 30.

A pressing groove 32 having a radius of curvature corresponding to the radius of curvature R ₁₁ (see FIG. 4) of the back surface portion 11 of the rack 8 to be manufactured is formed on the lower surface of the pressing die 31. In a state in which the bend portion that becomes the back surface portion 11 is fitted in the push groove 32, it is strongly pressed toward the sizing uneven surface portion 30. Therefore, with the sizing die 29 and the pressing die 31 shown in FIG. 5 (F) sufficiently close to each other, the rack teeth 10 are completed after the completion shown in FIG. 6 (B). At the same time as the state (the shape and dimensions are appropriate and chamfering is provided at the edge of each tooth), the shape and dimensions of the back surface portion 11 are also appropriate. The surplus extruded as a result of the sizing performed in this way gathers at the two relief flat surface portions 28 and 28. Accordingly, the flat surface portions 28 and 28 are hardly left in the completed rack 8. However, since the surplus does not press the sizing uneven surface portion 30 or the inner surface of the pressing groove 32 extremely strongly, not only the processing load of the sizing can be kept low, but also the sizing die 29 and It is easy to ensure the durability of the pressing die 31.

The rack 8 obtained as described above as shown in FIGS. 1 to 4 can sufficiently secure the width dimension, strength, and rigidity of the rack teeth 10 as described above. The outer diameter of the portion other than the portion formed with 10 is not unnecessarily large and is lightweight.
In the above-described embodiment, the case where the rack teeth 10 are processed in one behavior in the process of (C) → (D) in FIG. 5 has been described. However, this process is performed in two stages. You can also do things. That is, first, the processing of (A) → (B) in FIG. 7 is performed with a tooth forming punch having a shape corresponding to a pressure angle smaller than the pressure angle of the rack tooth to be obtained. A base rack tooth having a shape shorter than the rack tooth 10 to be obtained and having a shape indicated by a chain line in FIG. Next, by pressing a tooth finishing punch having a shape corresponding to the pressure angle of the rack tooth to be obtained against the portion to be the rack tooth, the rack tooth 10 indicated by the solid line in FIG. 7C and FIG. 8 is formed. . In the process of (B) → (C) in FIG. 7, the metal material present on the side surface of each tooth, indicated by the oblique lattice in FIG. 8, is moved toward the tip of each tooth. Thereafter, the sizing described above is performed.
If the processing of the rack teeth 10 is performed in two steps as described above, the stress applied to the tooth forming punch for forming the rack teeth can be kept small in each step, and the durability of the tooth forming punch can be reduced. Can be secured. Moreover, it is easy to ensure the accuracy of the rack teeth obtained.

  Further, the sizing may be performed in two stages as shown in FIG. 9 instead of one behavior as shown in (E) → (F) of FIG. In the sizing shown in FIG. 9, first, as shown in FIG. 9A, the base rack 27 is strongly held between the sizing die 29a and the pressing die 31a, and the shape of the rack teeth 10 is adjusted. Thereafter, as shown in (B), the base rack 27 is strongly sandwiched again between the receiving die 34 and the pressing die 35 provided with the receiving concave and convex portion 33 meshing with the rack teeth 10 on the upper surface, and the rear portion The shape and dimensions of 11 are adjusted to form a rack 8. Collecting surplus material that moves with sizing in the two relief flat surface portions 28 and 28 is the same as in the case of one behavior.

[Second Example of Embodiment]
10 to 11 show a second example of an embodiment of the present invention corresponding to claim 1 . In the case of this example, the amount of processing in the upsetting process shown in FIGS. 10A to 10B is made larger than that in the first example of the above-described embodiment, and this upsetting process The width of the obtained intermediate material 20a is made wider than in the case of the first example. Further, the radius of curvature of the partial cylindrical surface portion 17a is also made larger than in the case of the first example.

  In the case of this example, the intermediate material 20a as described above is pushed into the holding hole 22 of the die 21 while plastically deforming both ends in the width direction as shown in FIG. 10 (C) → (D). . This die 21 is the same as that used in the first example. However, when the intermediate material 20a is pushed into the holding hole 22 because the width of the intermediate material 20a is large, both ends of the intermediate material 20a in the width direction are connected to the inner side surfaces 24, 24 of the holding hole 22. It is handled by a continuous part with the guide inclined surface parts 25, 25. As a result, the cross-section of the intermediate material 20a while the metal material of the portion indicated by the oblique lattice in FIG. 11 existing at both ends in the width direction is moved upward toward the portion indicated by the oblique lattice in the upper portion as well. However, it changes from the shape represented by the chain line in FIG. 11 to the shape represented by the solid line. Then, after the intermediate material 20a is pushed into the back end of the holding hole 22, the rack teeth 10 are formed on the intermediate material 20a to form the raw rack 27a.

As is clear from the comparison between (C) and (D) in FIG. 5 and (C) and (D) in FIG. 10 described above, or the comparison between the chain line and the solid line in FIG. The width dimension of the portion where the rack tooth 10 is to be formed can be increased by pushing into the holding hole 22 while handling both ends in the width direction. For this reason, the width dimension of this rack tooth 10 is securable.
Since the configuration and operation of other parts are the same as those in the first example of the above-described embodiment, overlapping illustrations and descriptions are omitted.

[First example of reference example related to the present invention]
FIG. 12 shows a first example of a reference example related to the present invention. In the case of this reference example, as shown in FIGS. 12A to 12B, the outer diameter of the material 13 is partially reduced in the axial direction by performing a handling process that passes the material 13 through the die 36. Shrink except. And it is set as the preliminary intermediate material 37 whose outer diameter of a part of axial direction is larger than the outer diameter of the remainder of an axial direction, and in the axial direction part of this preliminary | backup intermediate material 37, the 1st example of embodiment mentioned above or Then, the same plastic working as in the second example of the embodiment described above is performed to obtain a rack 8a as shown in FIG. In the case of this reference example, the diameter of the portion of the rack 8a that is axially deviated from the portion where the rack teeth 10 are formed can be made smaller, and the entire rack 8a can be made lighter.

[Second example of reference example related to the present invention]
FIG. 13 shows a second example of a reference example related to the present invention. In the case of this reference example, as shown in FIGS. 13A to 13B, the material 13 is subjected to upsetting as shown in FIGS. 5A to 5B, for example. The material 20 is used. Then, as shown in FIG. 13C, the intermediate material 20 is subjected to a handling process through which the die 36 is passed, so that the outer diameter of the intermediate material 20 is reduced except for a part in the axial direction. And it is set as the 2nd intermediate material 38 whose outer diameter of a part of axial direction is larger than the outer diameter of the remainder of an axial direction, and this 2nd intermediate material 38 is the 1st example of the embodiment mentioned above, or mentioned above. The same plastic working as in the second example of the embodiment is performed to obtain a rack 8a as shown in FIG. Also in the case of this reference example, the diameter of the portion of the rack 8a that is axially deviated from the portion where the rack teeth 10 are formed can be made smaller to make the entire rack 8a lighter.

[Third example of embodiment]
14 to 18 show a third example of the embodiment of the invention corresponding to claims 1 and 3 .
In the case of the rack 8b of this example, the rod portion 9a is formed by combining the outer layer body 39 and the inner layer body 40. Of these, the outer layer body 39 is formed in a circular tube shape from a first type of metal material having excellent strength and wear resistance, such as carbon steel and stainless steel. Further, the inner layer body 40 is made in the shape of a circle from a lightweight second type metal material such as an aluminum alloy or a magnesium alloy. Of the outer layer body 39 and the inner layer body 40, the outer layer body 39 has a length dimension corresponding to the rack 8b to be manufactured, whereas the inner layer body 40 should form the rack teeth 10 on the outer peripheral surface. The length is limited to a length corresponding to a part of the length in the axial direction (a little longer than a portion where the rack teeth 10 are formed with a margin). Such an inner layer body 40 and the outer layer body 39 are tightly fitted into the inner layer body 40 close to one end of the outer layer body 39 in the axial direction (left side in FIGS. 14 to 16) by shrink fitting or cold fitting. It is combined by fixing.

For example, (A) → (B) → (C) → (D) → (E) in FIG. 18 is used as the material 13a constituting the rod portion 9a, which is a combination of the outer layer body 39 and the inner layer body 40 as described above. ) → (F), the same plastic working as in the second example of the embodiment shown in FIG. 10 (or the first example of the embodiment shown in FIG. 5) is performed. The rack 8b is as described above.
According to such a structure and manufacturing method of this example, it is possible to sufficiently ensure the strength of the rack teeth 10 and reduce the weight of the entire rack 8b for the reasons described above.

[Fourth Example of Embodiment]
FIGS. 19-24 has shown the 4th example of embodiment of this invention corresponding to Claims 1-3 . The second example of the embodiment shown in FIGS. 10 to 11 is different from the second example of the embodiment shown in FIG. 10 in that the radius of curvature of the cross-sectional shape of the edge at both ends in the width direction of the raw rack teeth 43 is increased in the process of forming the rack teeth. In order to leave a pair of guide plane portions 41, 41 parallel to each other on both sides of the finished rack tooth 10, the guide planes 41 and 41 are adjacent to both guide planes 41 and 41. This is in that a pair of relief flat surface portions 42 and 42 that are inclined in a direction approaching each other as they are separated from the portions 41 and 41 are provided. Since the configuration, operation, and effects of the other parts are the same as those in the second example of the above embodiment, the explanation for the equivalent parts will be omitted or simplified, and the points different from the second example will be mainly described below. Explained.

  In the case of this example, when the intermediate material 20a is processed into the raw rack 27b in the process of (C) → (D) in FIG. 19, a pair of guide plane portions 41 and 41 parallel to each other, and both the guide plane portions. A pair of relief flat surface portions 42 and 42 adjacent to 41 and 41 are formed. Both of these relief flat surface portions 42, 42 are provided on the opposite side of the raw rack teeth 43 formed in a part of the intermediate material 20a in the circumferential direction with the both guide flat portions 41, 41 as a boundary, As the distance from both the guide flat portions 41 and 41 increases, the distance between the guide flat portions 41 and 41 decreases.

  A pair of molding flat surfaces parallel to each other on a part of both inner side surfaces of the holding hole 22a, which is a molding concave groove, formed in the die 21a in order to form such both relief flat surface portions 42, 42. 44 and 44 are provided with a pair of second molding flat surfaces 45 and 45 which are inclined in a direction in which the distance between the flat surfaces 44 and 44 becomes narrower as the distance from the molding flat surfaces 44 and 44 increases. ing. Then, in the process of (C) → (D) in FIG. 19, when the intermediate material 20a is processed into the raw rack 27b, both the reliefs are formed at portions corresponding to the second molding flat surfaces 45, 45. The flat surface portions 42 and 42 are formed to form the raw rack 27b as shown in FIG. That is, the raw rack 27b in which the raw rack teeth 43 are formed is obtained by the tooth forming punch 26a having a shape corresponding to a pressure angle smaller than the pressure angle of the rack teeth to be obtained.

  After that, as shown in FIGS. 20A to 20B, in a state where the both relief flat surface portions 42 and 42 are located between the pressing die 46 and the receiving die 47, which are a pair of molds. Then, plastic working is performed to increase the radius of curvature of the cross-sectional shape of the tooth root part or the tooth tip part at both ends in the width direction of the raw rack teeth 43. By this plastic working, the curvature radius of the tooth root part or the tooth tip part of the edge part of the width direction both ends of the raw rack tooth 43 is increased, and the edge part of the edge part of the width direction both ends of the raw rack tooth 43 is increased. Curved portions 48 and 48 as shown in FIG. 23B are formed in the tooth root portion or the tooth tip portion. Such curved surface portions 48 and 48 prevent the edge portions at both ends in the width direction of the completed rack tooth 10 from interfering with other members, and prevent stress concentration on the edge portions. It is provided for the purpose. This example is a process in which the raw rack teeth 43 shown in FIG. 23A are plastically processed into the rack teeth 10 shown in FIG. 23C, and the curved surface portion 48 as shown in FIG. By forming 48, the load on the mold used in the machining process for plastic processing of the rack teeth 10 is reduced, and the shape accuracy and dimensional accuracy of the rack teeth 10 obtained by preventing the occurrence of burrs are increased. I am trying to improve it. Further, in the case of this example, a virtual cylinder that extends the partial cylindrical surface by stopping the metal material that moves in accordance with the plastic working of the curved surface portions 48, 48 as described above, on the both escape flat surface portions 42, 42. Prevents excess wall from projecting radially outward than the surface.

  In addition, the curved surface part formed in the edge of the width direction both ends of the said bare rack tooth | gear 43 in the process shown to (A)-> (B) of said FIG. 20, and (A)-> (B) of FIG. The curvature radii of 48 and 48 are set larger than the curvature radii of the curved surface portions remaining at both ends in the width direction of the rack tooth 10 after completion. The reason for this is the step of finishing the raw rack teeth 43 into the rack teeth 10 shown in FIGS. 21 or 22 (A) → (B) and (B) → (C) of FIG. Thus, since the curvature radius of the curved surface portions 48, 48 of the edge portion or the tip portion of the edge portion in the width direction tends to be small, the curved surface remaining at both width direction ends of the rack tooth 10 after completion. This is to ensure the curvature radius of the part.

  The second intermediate material 49 having the curved surfaces 48 and 48 as described above is thereafter as shown in (A) → (B) of FIG. 21 or FIG. 22 as in the first example of the embodiment described above. The rack teeth 10 are formed by being pushed into the holding hole 22b of the die 21b by the tooth forming punch 26. At this time, the inner dimension of the holding hole 22b may be the same as the width dimension of the second intermediate material 49 as shown in FIG. 21, or slightly smaller than this width dimension as shown in FIG. May be. As shown in FIG. 22, when the inner dimension of the holding hole 22 b is made smaller than the width dimension of the second intermediate material 49, the width direction of the second intermediate material 49 is formed in the process of forming the rack teeth 10. The both guide plane portions 41, 41 existing at both ends are handled. In any case, the second intermediate material 49 is pushed into the holding hole 22b of the die 21b by the tooth forming punch 26, thereby forming the rack teeth 10 on one side surface in the circumferential direction and the both guides. A rack 8a in which the properties of the flat portions 41 and 41 are appropriate can be obtained.

  The rack 8a thus obtained can be used as it is, but sizing for improving the accuracy of the rack teeth 10 is performed as necessary. This sizing is basically performed in the same manner as in the first example of the embodiment described above. However, when it is necessary to ensure the accuracy of the two guide flat portions 41, 41, as shown in FIG. 24A, the guide flat portions 41, 41 are connected by a pair of holding surfaces 50, 50. Do it while holding down. On the other hand, if it is not necessary to ensure the accuracy of both guide flat portions 41, 41, the rack 8a may simply be pressed against the receiving die 34 as shown in FIG. The two guide flat portions 41, 41 are provided to prevent the rack 8a from being displaced in the rotational direction by engaging the linear portion of the guide sleeve with the rack 8a incorporated in the steering gear. ing. In addition, the basic configuration, operation, and effects are the same as those in the first example of the above-described embodiment.

[Fifth Example of Embodiment]
25 to 29 show a fifth example of the embodiment of the invention corresponding to claims 1 to 3 . This example shows a case where the structure of the third example of the embodiment shown in FIGS. 14 to 18 is manufactured by the manufacturing method of the fourth example of the embodiment described above. FIG. 25 showing this example corresponds to FIG. 19 showing the fourth example of this embodiment, FIG. 26 to FIG. 28 corresponding to FIG. 20 to 22 and FIG. 29 corresponding to FIG. According to such a structure and manufacturing method of this example, as in the third example of the above embodiment, the strength of the rack teeth 10 and the weight reduction of the entire rack 8b can be more sufficiently achieved, and the mold While reducing a burden, the shape accuracy and dimensional accuracy of the rack tooth 10 obtained can be made favorable.

  The rack of the present invention can be applied as a rack constituting the steering gear 5 as shown in FIG. 30 described above, and the cost and weight of the steering gear 5 can be reduced. However, the present invention is not limited to such a steering gear 5 but can be applied to racks incorporated in various mechanical devices, and can contribute to cost reduction and weight reduction of the mechanical devices.

The perspective view of the rack which shows the 1st example of embodiment of this invention. FIG. The same arrow view. FIG. 4 is an enlarged cross-sectional view of FIG. 3. Sectional drawing seen from the same direction as FIG. 4 which shows the manufacturing method of the structure of a 1st example in order of a process. The partial perspective view which shows the shape of the rack tooth before and behind sizing. The figure corresponding to the knee cross section of (D) of FIG. 5 which shows the shape change at the time of processing rack teeth in two steps. The expanded sectional view which shows the state of the shape change of the tooth | gear between (B) and (C) of FIG. Sectional drawing which shows the case where sizing is divided into two steps. The figure similar to FIG. 5 which shows the 2nd example of embodiment of this invention. Sectional drawing which shows the state of the shape change of the intermediate raw material between (C) and (D) of FIG. The partial cutting side view which shows the 1st example of the reference example relevant to this invention in process order. The partial cutting side view which shows the 2nd example in order of a process. The perspective view of the rack which shows the 3rd example of embodiment of this invention. FIG. The same arrow view. FIG. 17 is an enlarged toe cross-sectional view of FIG. 16. Sectional drawing seen from the same direction as FIG. 17 which shows one example of the manufacturing method of the structure of a 3rd example in process order. Sectional drawing in the 4th example of an embodiment of the invention showing from the 1st plastic working thru / or the previous stage of the 2nd plastic working in order of a process as seen from the same direction as FIG. Similarly, in the same direction as FIG. 4, the plastic processing for increasing the radius of curvature of the cross-sectional shape of the tooth root part or the tooth tip part at both ends in the width direction of the raw rack tooth performed in the previous stage of the second plastic working is shown in the same direction as FIG. FIG. FIG. 5 is a cross-sectional view seen from the same direction as in FIG. 4, showing a first example of plastic working in the order of the steps, in which the shape of the raw rack teeth is adjusted to form rack teeth after the second plastic working. Sectional drawing which looked at the 2nd example from the same direction as FIG. 4 which shows the 2nd example in process order. The shape of the raw rack teeth or rack teeth as the machining progresses is shown. (A) shows the raw rack teeth at the end of the previous stage of the second plastic working, and (B) shows the width direction ends of the raw rack teeth. (C) is a partial perspective view which shows the state after performing the plastic working which enlarges the curvature radius of the cross-sectional shape of an edge, respectively, and the rack tooth after sizing. Sectional drawing seen from the same direction as FIG. 4 which shows two examples of the implementation state of sizing. Sectional drawing seen from the same direction as FIG. 4 which shows to the prior | preceding stage of 1st plastic processing thru | or 2nd plastic working in 5th example of embodiment of this invention. FIG. 4 is a cross-sectional view seen from the same direction as FIG. 4, showing the plastic processing for increasing the radius of curvature of the cross-sectional shape of the edge of both ends in the width direction of the raw rack teeth, performed in the same stage as the second plastic processing. . FIG. 5 is a cross-sectional view seen from the same direction as in FIG. 4, showing a first example of plastic working in the order of the steps, in which the shape of the raw rack teeth is adjusted to form rack teeth after the second plastic working. Sectional drawing which looked at the 2nd example from the same direction as FIG. 4 which shows the 2nd example in process order. Sectional drawing seen from the same direction as FIG. 4 which shows two examples of the implementation state of sizing. The side view which shows an example of the steering device for motor vehicles provided with the steering gear incorporating the rack used as the object of this invention.

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3 Universal joint 4 Intermediate shaft 5 Steering gear 6 Input shaft 7 Tie rod 8, 8a, 8b Rack 9, 9a Rod part 10 Rack tooth | gear 11 Back part 12 Circular collar part 13, 13a Material 14 Receiving type 15 Concave Groove portion 16 Press punch 17, 17a Partial cylindrical surface portion 18 Flat surface portion 19 Curved surface portion 20, 20a Intermediate material 21, 21a, 21b Die 22, 22a, 22b Holding hole 23, 23a Bottom portion 24 Inner side surface 25 Guide inclined surface portion 26, 26a Tooth molding Punch 27, 27a, 27b Raw rack 28 Escape flat surface portion 29, 29a Sizing die 30 Sizing uneven surface portion 31, 31a Stamping die 32 Pushing groove 33 Receiving recessing portion 34 Receiving die 35 Stamping die 36 Die 37 Preliminary intermediate material 38 Second Intermediate material of 39 Sotai 40 inner body 41 guide the flat surface portion 42 flank flat portion 43 containing the rack teeth 44 forming a flat surface 45 second moldable flat surface 46 pressing die 47 receiving die 48 curved portion 49 second intermediate material 50 clamping surfaces

Claims (3)

It is made of a metal material and is formed by plastic working on a rod part with a circular cross section whose solid part is a solid material at least in the axial direction and one radial side surface of a part that is a solid material in a part of the axial direction of this rod part. The portion of the outer peripheral surface of the portion that is a solid material in a part in the axial direction has a radius of curvature of the cross-sectional shape of a portion that deviates in the circumferential direction from the portion in which the rack tooth is formed. A manufacturing method of a rack that is larger than the radius of curvature of the cross-sectional shape of the outer peripheral surface of the remaining axial direction,
While crushing a part in the axial direction and a part in the circumferential direction to a part in the axial direction of the rod-shaped material to be the rod part, a part in the axial direction and in the circumferential direction The remaining part is subjected to a first plastic working to form a partial cylindrical surface having a radius of curvature larger than the radius of curvature of the outer peripheral surface of the material to obtain an intermediate material, and the circle in a part of the intermediate material in the axial direction. The rack teeth are formed in a part of the circumferential direction by second plastic working,
In the first plastic working, a part of the axial direction of the material is crushed in the radial direction, so that a part of the outer peripheral surface of the part in the axial direction to form rack teeth is a flat part. Is the upsetting process in which the remaining part deviated from the above is a partial cylindrical surface in which the radius of curvature of the cross-sectional shape is larger than the radius of curvature of the cross-sectional shape of the outer peripheral surface of the material,
The second plastic working is deviated from the plane part at a part in the axial direction of the intermediate material by a holding hole of a die whose inner surface interval is smaller than the outer diameter of the intermediate material in the width direction of the plane part. While supporting the remaining portion, pressing the tooth forming punch having an uneven shape corresponding to the rack tooth to be formed against the flat surface portion and pushing the intermediate material into the holding hole, the width of both ends of the intermediate material is reduced. A method for manufacturing a rack, which is press working for forming rack teeth on a flat portion while moving a metal material to the flat portion. It is made of a metal material and is formed by plastic working on a rod part with a circular cross section whose solid part is a solid material at least in the axial direction and one radial side surface of a part that is a solid material in a part of the axial direction of this rod part. The portion of the outer peripheral surface of the portion that is a solid material in a part in the axial direction has a radius of curvature of the cross-sectional shape of a portion that deviates in the circumferential direction from the portion in which the rack tooth is formed. A manufacturing method of a rack that is larger than the radius of curvature of the cross-sectional shape of the outer peripheral surface of the remaining axial direction,
While crushing a part in the axial direction and a part in the circumferential direction to a part in the axial direction of the rod-shaped material to be the rod part, a part in the axial direction and in the circumferential direction The remaining part is subjected to a first plastic working to form a partial cylindrical surface having a radius of curvature larger than the radius of curvature of the outer peripheral surface of the material to obtain an intermediate material, and the circle in a part of the intermediate material in the axial direction. The second plastic working for forming the rack teeth in a part of the circumferential direction is performed in a plurality of stages, and the raw rack teeth are formed by a tooth forming punch having a shape corresponding to a pressure angle smaller than the pressure angle of the rack teeth to be obtained. After forming, plastic processing is performed to increase the curvature radius of the cross-sectional shape of at least the tooth root part or the edge part of the tooth tip part at both ends in the width direction of the raw rack tooth, and then the pressure angle of the rack tooth to be obtained is obtained. A matching tooth finish punch is pushed onto this bare rack tooth. Put it, to process this element rack teeth on the rack teeth, the rack manufacturing method of. It is made of a metal material and is formed by plastic working on a rod part with a circular cross section whose solid part is a solid material at least in the axial direction and one radial side surface of a part that is a solid material in a part of the axial direction of this rod part. The portion of the outer peripheral surface of the portion that is a solid material in a part in the axial direction has a radius of curvature of the cross-sectional shape of a portion that deviates in the circumferential direction from the portion in which the rack tooth is formed. A manufacturing method of a rack that is larger than the radius of curvature of the cross-sectional shape of the outer peripheral surface of the remaining axial direction,
While crushing a part in the axial direction and a part in the circumferential direction to a part in the axial direction of the rod-shaped material to be the rod part, a part in the axial direction and in the circumferential direction The remaining part is subjected to a first plastic working to form a partial cylindrical surface having a radius of curvature larger than the radius of curvature of the outer peripheral surface of the material, thereby forming an intermediate material. Sizing for improving the accuracy of the rack teeth after forming the rack teeth on a part of the circumference in the axial direction and forming a pair of relief flat surface portions on both sides of the rack teeth. The metal material that moves along with this sizing is stopped at the two escape flat surfaces, and the excess wall is prevented from projecting radially outward from the virtual cylindrical surface extending the partial cylindrical surface. Production method.

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